(bash.info) Definitions

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(bash.info) Basic Shell Features

 
 2 Definitions
 *************
 
 These definitions are used throughout the remainder of this manual.
 
 `POSIX'
      A family of open system standards based on Unix.  Bash is
      primarily concerned with the Shell and Utilities portion of the
      POSIX 1003.1 standard.
 
 `blank'
      A space or tab character.
 
 `builtin'
      A command that is implemented internally by the shell itself,
      rather than by an executable program somewhere in the file system.
 
 `control operator'
      A `token' that performs a control function.  It is a `newline' or
      one of the following: `||', `&&', `&', `;', `;;', `|', `|&', `(',
      or `)'.
 
 `exit status'
      The value returned by a command to its caller.  The value is
      restricted to eight bits, so the maximum value is 255.
 
 `field'
      A unit of text that is the result of one of the shell expansions.
      After expansion, when executing a command, the resulting fields
      are used as the command name and arguments.
 
 `filename'
      A string of characters used to identify a file.
 
 `job'
      A set of processes comprising a pipeline, and any processes
      descended from it, that are all in the same process group.
 
 `job control'
      A mechanism by which users can selectively stop (suspend) and
      restart (resume) execution of processes.
 
 `metacharacter'
      A character that, when unquoted, separates words.  A metacharacter
      is a `blank' or one of the following characters: `|', `&', `;',
      `(', `)', `<', or `>'.
 
 `name'
      A `word' consisting solely of letters, numbers, and underscores,
      and beginning with a letter or underscore.  `Name's are used as
      shell variable and function names.  Also referred to as an
      `identifier'.
 
 `operator'
      A `control operator' or a `redirection operator'.  
      Redirections, for a list of redirection operators.  Operators
      contain at least one unquoted `metacharacter'.
 
 `process group'
      A collection of related processes each having the same process
      group ID.
 
 `process group ID'
      A unique identifier that represents a `process group' during its
      lifetime.
 
 `reserved word'
      A `word' that has a special meaning to the shell.  Most reserved
      words introduce shell flow control constructs, such as `for' and
      `while'.
 
 `return status'
      A synonym for `exit status'.
 
 `signal'
      A mechanism by which a process may be notified by the kernel of an
      event occurring in the system.
 
 `special builtin'
      A shell builtin command that has been classified as special by the
      POSIX standard.
 
 `token'
      A sequence of characters considered a single unit by the shell.
      It is either a `word' or an `operator'.
 
 `word'
      A sequence of characters treated as a unit by the shell.  Words
      may not include unquoted `metacharacters'.
 

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(bash.info) Basic Shell Features